WO1997040965A1

WO1997040965A1 - A tool for a demolition hammer or the like

Info

Publication number: WO1997040965A1
Application number: PCT/EP1997/002055
Authority: WO
Inventors: Giovanni Battista Andrina
Original assignee: Corimag SRL
Current assignee: Corimag SRL
Priority date: 1996-04-26
Filing date: 1997-04-23
Publication date: 1997-11-06
Anticipated expiration: 1998-10-26
Also published as: AU2388897A; ITTO960097U1; ITTO960097V0; ZA973651B; IT239729Y1

Abstract

A tool for a demolition hammer or the like comprises an elongate body (1) having an attachment end (3) for connection to the hammer actuator and a working tip (5). The elongate body (1) has grooves (7) in its outer surface which extend from the working tip (5).

Description

A tool for a demolition hammer or the like

The present invention relates to tools for demolition hammers

or the like used in general in roadworks, building work, in

quarries or mines, in foundries, for demolition work, breaking

up, piercing or excavating materials of various types such as,

for example, asphalt, concrete, rock, foundry slag, tiles,

etc. Such tools may be used with small, manually operated,

pneumatic or electric drills or hammers or with heavy equipment, even of several tons' weight, controlled fluid-

dynamically and associated with earth-moving equipment or like

movable plant.

More particularly, the invention relates to a tool for a demolition hammer or the like which comprises an elongate body having an attachment end for connection to the hammer actuator

and a working tip.

Tools of the known type indicated above are subject to very

serious stress in use. In particular, the attachment end is

subject to the direct percussive action of a beater mass

reciprocated within the actuator while the working tip is

subject to impacts with the material being worked. Such tools are generally made from heat-treated steel alloys,

possibly with parts of composite materials such as sintered ceramics.

Normally these tools have a cylindrical body with, for

example, a circular or hexagonal section, which extends to the working tip which may be shaped like a chisel, cone or pyramid, or may be flat, depending on the work the tool is

intended to carry out and the material being worked.

The elongate body and its working tip are usually made by hot

or cold pressing or by mechanical working by milling of a

metal bar.

Once the desired shape of the body has been formed it is then

hardened by heat treatment at about 850°C and subsequent

tempering at about 300°C to toughen the tool.

In use, however, such tools, exactly because of the high stress to which they are subject, tend to overheat,

particularly at the working tip, which may even reach

temperatures of the order of 600°C or more, which softens the

tool and results in the partial or total loss of the hardening. This problem must be attributed mainly to the

cylindrical shape of the known tools, which does not enable

the heat which builds up in use to disperse effectively.

Moreover, when the working tip of the tool penetrates the

material being worked, forming a hole therethrough, detritus from the material accumulates in the bottom and at the sides of the hole in the form of dust and/or chips and forms a sort

of cushion between the material which has yet to be worked and

the working tip of the tool which damps the impacts of the tool, opposing further penetration into the material.

Because of the presence of this cushion and high overheating,

which also results from the fact that the cushion absorbs some of the energy from the impact of the tool, prior-art tools

wear rapidly whereby their working tips become blunted and not

very effective so that their penetrating characteristics fall

off and they have a short useful life.

In an attempt to avoid these problems, valued materials, such

as steel alloys containing relatively high percentages of very durable metals such as nickel, chromium, vanadium or tungsten,

are used to make these tools which are thus very expensive. In order to avoid the problems mentioned above, the present

invention provides a tool of the type defined at the beginning

of the description, characterised in that the elongate body

has at least one elongate recess in its outer surface, the

recess extending from the working tip.

By virtue of this solution, the tool of the invention has a shape which effectively facilitates heat exchange whereby, in

use, it is less subject to the overheating which can cause

loss of hardness .

Moreover, the presence of the or each recess provides an

effective pathway for the escape of detritus formed by the breaking up of the material so that this does not accumulate

between the working tip and the material but is expelled by virtue of the movement of the tool, considerably improving the ability of the tool to penetrate the material. More

particularly, the life of the tool is lengthened considerably since the wear it incurs per unit working time is reduced.

The use of a tool according to the invention is also beneficial to the life of the hammer actuator with which it is used since, by virtue of the fact that the tool penetrates the

material better, it transmits fewer reactive blows to the

actuator.

According to a preferred characteristic of the invention, the

at least one elongate recess comprises a plurality of grooves .

The formation of these grooves in the outer surface of the

tool gives it a shape which enhances the uniformity and

rapidity of distribution of the hardening, the entire section of the tool in the zone including the grooves being hardened whereas, in known tools the hardening occurs mainly in the outermost part of the tool section. By virtue of the fact

that the hardening is distributed more uniformly and more rapidly, a less severe hardening medium, for example oil instead of water, may be used for the hardening treatment, thus reducing the risk of the tool deforming or cracks forming

in it.

Moreover, as the effect of the hardening treatment is

improved, steels which are less rich in alloying elements may be used to form such a tool, all of which improves the economy of production, while providing a tool which has a better

penetrating capacity than known tools .

As the working end of the tool is subject to less heat and

more uniform hardening, this end does not deform appreciably

in use but, as a result of the inevitable wear, is worn away

gradually, the original profile of the working tip remaining

substantially unchanged, the tool thus having a self-

sharpening property.

Further characteristics and advantages of the invention will

become clearer from the detailed description which follows,

provided purely by way of non-limitative example with

reference to the appended drawings, in which:

Figure 1 is a perspective view of a tool according to

the invention,

Figures 2 and 3 are side elevations of the tool of

Figure 1, staggered by 90° about the axis of the tool, and

Figure 4 is a cross-sectioned elevational view taken on

the line IV-IV of Figure 1.

With reference to the drawings, a tool for a demolition hammer

or the like is generally indicated 1. The generally cylindrical elongate body of the tool 1, for example, with a

circular or hexagonal section, is made from steel, possibly

with parts of steel-based composite and sintered ceramics.

The tool 1 has an attachment end 3, occupying about a third of

its total length, for connection to the hammer actuator (not illustrated in the drawings) and intended to be received

within the actuator and an opposite, working end or tip 5

which may be shaped in various ways according to the type of

work to be carried out and the type of material to be worked, for example being in the form of a chisel, cone or pyramid or

being flat. A tool 1 having a chisel-shaped working tip 5 is

shown in the drawings .

At least one groove 7 extends in the outer surface of the tool

1 from the working tip 5 towards the attachment end 3. This

groove may extend axially along the body of the tool 1 or may have a slight helical curvature around the surface of the tool

Preferably the surface of the body 1 has a plurality of grooves 7 equiangularly spaced about its axis A, for example

there being four such grooves . Each groove 7 is bounded by a pair of opposing side faces 9

and a bottom 11 which is suitably curved so as to fillet the

bases of the opposed faces 9 to avoid cracks forming at the bases of the faces 9.

Each groove 7 preferably extends through only part of the

axial length of the tool 1 and has at least one portion 15 the

bottom of which is inclined to a plane through the axis A of

the tool 1.

In the preferred embodiment shown in the drawings, each groove 7 has a straight axial portion 13 which extends from the working tip 5 and another axial portion 15 inclined to the

axis A of the body 1 so as to connect the straight portion 13 to the outer surface of the body 1.

Each groove 7 is separated from the adjacent grooves 7 by an

axial rib 18 which projects radially from a central core 20 of

the elongate body 1. This core has a cross-section which may

be likened to a generally circular area, the diameter of

which, in correspondence with the straight portions 15 of the bottoms of the grooves 7, is between about one third and about two thirds of the diameter of the area of the outer section of

the tool 1 and is preferably about half the diameter of the

outer section of the elongate body 1.

When the elongate body 1 has a chisel-shaped working tip, it

has a cutting edge 5a transverse the axis A. In this case, the elongate body 1 conveniently has two pairs of grooves 7,

each pair located on one side of the cutting edge 5a. The rib 18 which separates those grooves 7 on the same side of the

cutting edge 5a has an end portion 18a adjacent the cutting

edge 5a which is inclined to the axis A. Thus the working tip

5 wears gradually, in use, always retaining substantially the

same shape as a result of the wear which means that the

penetrating ability of the tool 1 remains constant with time.

By virtue of the conformation of the tool of the invention, it has a shape close to the working tip 5 which means that it hardens uniformly throughout its section. This zone of the tool is thus very hard which makes it more capable of withstanding the repeated impacts with the material to be

worked without its original profile being changed appreciably. In that zone of the tool in correspondence with the end

portions of the inclined portions 15 of the grooves and in

that zone close to the attachment end 3 where the section of

the tool is cylindrical or almost cylindrical, hardening

occurs mainly at the surface so that this portion of the tool

1 is less hard and the attachment end 3 has better toughness

characteristics, which enables it to withstand the compressive

and flexural stresses to which this portion of the tool is

subject more effectively, avoiding the tendency for cracks to

form or for this portion of the tool to distort.

Claims

1. A tool for a demolition hammer or the like, comprising

an elongate body (1) having an attachment end (3) for

connection to the hammer actuator and a working tip (5) ,

characterised in that the elongate body (1) has at least

one elongate recess (7) in its outer surface, this recess (7)

extending from the working end (5) .

2. A tool according to Claim 1, characterised in that the at least one elongate recess consists of a plurality of grooves (7) .

3. A tool according to Claim 2, characterised in that the grooves (7) extend substantially axially along the elongate body (1) .

4. A tool according to Claim 2 or Claim 3, characterised in that the grooves (7) are each bounded by a pair of symmetrical

side faces (9) and a bottom (11) shaped so as to fillet the

bases of the side faces (9) . E 055

12

5. A tool according to any one of Claims 2 to 4 ,

characterised in that the grooves (7) extend through part of

the axial length of the elongate body (1) from the working tip

(5) .

6. A tool according to any one of Claims 2 to 4, characterised in that the grooves (7) are equiangularly spaced

about the axis (A) of the elongate body (1) .

7. A tool according to Claim 6, characterised in that the

bottom (11) of each groove (7) has an axial portion (15)

inclined to the axis (A) of the elongate body (1) .

8. A tool according to Claim 7, characterised in that the bottom (11) of the groove (7) has a straight portion (13)

which extends from the working tip (5) and terminates at the

axial inclined portion (15) which connects it to the radially

outer surface of the elongate body (1) .

9. A tool according to Claim 8, characterised in that the

grooves (7) are separated by ribs (18) which project from a

central core (20) of the elongate body (1) , this core (20) having a generally circular cross-section, the diameter of which, in correspondence with the straight portions (13) of the bottoms (11) of the grooves (7) , is between about one

third and about two thirds of the diameter of the

substantially circular outer section of the elongate body (1) .

10. A tool according to Claim 9, characterised in that the

diameter of the generally circular cross-section of the

central core (20) of the elongate body (1) is approximately half the diameter of the substantially circular outer section

of the elongate body (1) .

11. A tool according to any one of the preceding claims, characterised in that the elongate body (1) has a chisel- shaped working tip with a cutting edge (5a) transverse the axis (A) of the elongate body (1) , in which the elongate body

(1) has two pairs of grooves (7) , each pair being disposed on one side of the cutting edge (5a) , the grooves (7) of each pair being separated from each other by an axial rib (18)

having an end portion (15a) adjacent the cutting edge (5a)

inclined to the axis (A) of the elongate body (1) .